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Issue 21, 2018
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Pyridine-terminated low gap π-conjugated oligomers: design, synthesis, and photophysical response to protonation and metalation

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Abstract

Reported here is the design and synthesis of among the first pyridine terminated acceptor–donor–acceptor–donor–acceptor (A–D–A–D–A) based π-conjugated oligomers, EH_DPP_2T_Pyr (1), EH_II_2T_Pyr (2), and EH_II_1T_Pyr (3). The molecules incorporate thiophenes as electron donors, isoindigo/diketopyrrolopyrrole as electron acceptors, and are capped with pyridine, a weak electron acceptor, on both ends. All target oligomers show attractive photophysical properties, broad absorption in the visible region (λmax = 636 nm, 575 nm, and 555 nm, for 1, 2, and 3, respectively) and emission which extends to the IR region (emission λmax = 734 nm and 724 for 1 and 2, respectively). Given the pyridine nitrogens, the optoelectronic properties of the compounds can be further tuned by protonation/metalation. All compounds show a bathochromic shift in visible absorption and fluorescence quenching upon addition of trifluoroacetic acid (TFA). Similar phenomena are observed upon addition of metals with a particularly strong response to Cu2+ and Pd2+ as indicated by Stern–Volmer analysis (e.g., for Pd2+; Ksv = 7.2 × 104 M−1 (λ = 673 nm), 8.5 × 104 M−1 (λ = 500 nm), and 1.1 × 105 (λ = 425 nm) for 1, 2, and 3, respectively). The selective association of the molecules to Cu2+ and Pd2+ is further evidenced by a color change easily observed by eye and under UV light, important for potential use in colorimetric sensing.

Graphical abstract: Pyridine-terminated low gap π-conjugated oligomers: design, synthesis, and photophysical response to protonation and metalation

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Article information


Submitted
05 Sep 2018
Accepted
30 Sep 2018
First published
01 Oct 2018

Org. Chem. Front., 2018,5, 3170-3177
Article type
Research Article
Author version available

Pyridine-terminated low gap π-conjugated oligomers: design, synthesis, and photophysical response to protonation and metalation

A. O. Weldeab, L. Li, S. Cekli, K. A. Abboud, K. S. Schanze and R. K. Castellano, Org. Chem. Front., 2018, 5, 3170
DOI: 10.1039/C8QO00963E

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